Switching to a launcher: Yes it should, its big and bulky.

Switching to your sidearm shouldn't bring you to a halt... At the very least, it should revert you to a walk while the animation plays out. The same goes for switching to your rifle.

A better option would be to switch to your pistol in combat pace, and switching to your rifle in a walk.

The problem is compounded when running from enemy fire, only to accidentally hit the switch key and come to a stop (bullets raining down all around)and get killed.